A wide variety of antenna matching circuits are known in the art of wireless radio communications. Such matching circuits must provide good impedance matching, and thus efficient energy transfer, between an antenna and transmitter/receiver circuits at a particular design frequency or, more commonly, over a design frequency band. When used in portable communication devices, antennas and matching circuits must typically meet additional constraints with regard to their size and weight.
PCT patent publication WO 98/07208, which is incorporated herein by reference, describes an antenna matching circuit produced using printed circuit techniques. The circuit includes an inductor and capacitor which are formed by printing conductive material on a dielectric substrate. The inductor is made of a serpentine or spiral conductive strip on one side of the substrate. The capacitor is formed by parallel conductive plates on opposing surfaces of the substrate. The matching circuit is integrated with an antenna for use with a wireless modem, which plugs into a PCMCIA slot of a portable computer.